Halitosis, or oral malodour, is thought to be created by degraded epithelial cells of the tongue and the surface of the oral mucosa. Volatile sulphur compounds (such as hydrogen sulphide, methyl mercaptan, dimethyl sulphide) are produced by the putrefactive activities of bacteria in the saliva, the gingival crevice, the tongue coating and other places in the oral cavity. Tongue coating includes desquamated epithelial cells released from the oral mucosa, leukocytes from periodontal pockets, and bacteria. Leukocytes possess large quantities of sulphur-containing amino acids from which volatile sulphur compounds are made.
There have been many commercial attempts to reduce or mask oral malodour, including mouthwash and chewing gum. Their effects last perhaps a few hours.
The simplest method of removing the volatile sulphur compounds is to scrape the tongue (by brush or tongue scraper, for example). But this method has disadvantages. For example, scraping damages the oral mucosa (because the cells are strongly attached to the oral mucosa) and also produces a gag reflex if the dorsal portion of the tongue is touched.
PCT application #US91/06011 (Chaykin) discloses a method for reducing the undesirable side effects of eating vegetables like onions, garlic and beans; namely, ingesting active dry yeast in a form which retains substantial enzymatic activity under digestive conditions in the stomach and intestinal tract.
It is known informally that Bacillus Natto has been placed on the tongue during the day but that it had no or little effect on oral malodour.